Splenic Artery Aneurysm

A splenic artery aneurysm is a dilatation of the splenic artery to 1.5 times the normal diameter, usually over 10 mm. It is the commonest visceral artery aneurysm, about 60% of the total.

It is found in 0.1 to 1% of angiograms, and in up to 10% of older people at autopsy. Women are affected about four times as often as men, and about 20% are multiple.

Risk factors are multiparity and pregnancy, portal hypertension and splenomegaly (10 to 30% of cirrhosis), liver transplantation, fibromuscular dysplasia and atherosclerosis. Pancreatitis, trauma and infection cause pseudoaneurysms.

Rupture risk is about 2% overall, and higher with pseudoaneurysm, pregnancy and portal hypertension. In pregnancy rupture carries a maternal mortality of about 20 to 70% and foetal mortality of about 70 to 90%.

Pathophysiology. Medial degeneration, with hormonal weakening of the elastic lamina (oestrogen, progesterone, relaxin) and increased flow in pregnancy and portal hypertension, produces a saccular aneurysm at the bifurcation.

Rupture can have two phases. Initial bleeding is contained in the lesser sac, followed by temporary stability and then free rupture into the peritoneum (the double rupture phenomenon).

• Asymptomatic in about 80%. Found on imaging or plain film as a ring calcification in the left upper quadrant.
• Left upper quadrant or epigastric pain, sometimes radiating to the left shoulder, with nausea.
• Rupture: sudden severe abdominal pain, hypotension and shock, or gastrointestinal bleeding with erosion into the stomach, bowel or pancreatic duct.
• Pregnancy: rupture in the third trimester or at delivery is often the first presentation.

Red flags.

• Pregnancy, or a woman of childbearing age
• Sudden pain with transient improvement then collapse (double rupture)
• Pseudoaneurysm with pancreatitis
• Portal hypertension or liver transplant candidate
• Diameter of 20 mm or more, or growth of 5 mm or more in a year

• Ultrasound with colour Doppler. Screening for a cystic structure with turbulent flow, and surveillance.
• CT angiography. Size, neck, number, wall calcification, thrombus, and relation to the pancreas and splenic hilum. MR angiography without gadolinium in pregnancy.
• Catheter angiography when treatment is planned.
• Abdominal X-ray. A curvilinear or ring calcification.
• Cause workup. Liver disease and portal hypertension assessment, pregnancy test, imaging for fibromuscular dysplasia, amylase and lipase.

Differential diagnosis.

• Pancreatic pseudocyst and cystic pancreatic neoplasm
• Splenic cyst and splenic infarct
• Tortuous splenic artery
• Splenic vein aneurysm and splenic artery arteriovenous fistula
• Adrenal, renal or gastric mass
• Calcified lymph node

Indications for treatment. Symptoms, pseudoaneurysm, any size in pregnancy or when pregnancy is planned, 20 mm or more in other patients, growth of 5 mm or more in a year, portal hypertension with a liver transplant planned, and rupture.

Surveillance. Under 20 mm without risk features: imaging every 12 months, and every 2 years when stable. Women of childbearing age are treated, not observed.

Elective treatment.

• Endovascular repair first: coil embolisation proximal and distal to the aneurysm (sandwich technique), covered stents or vascular plugs for proximal lesions. For hilar aneurysms embolisation can infarct part of the spleen.
• Post-embolisation syndrome (fever, left upper quadrant pain and ileus, 3 to 7 days) is managed with paracetamol 1 g orally every 6 hours (maximum 4 g daily, 3 g in liver impairment or under 50 kg). Antibiotic prophylaxis cefazolin 2 g intravenously as a single dose before the procedure. Splenic abscess is a late risk.
• Surgery (laparoscopic or open) for ligation, aneurysmectomy or splenectomy for hilar aneurysms and failed embolisation. Splenectomy needs vaccination at least 2 weeks before elective surgery (pneumococcus, Haemophilus influenzae type b, meningococcus groups A, C, W, Y and B) and penicillin V 250 mg orally twice daily lifelong for age 5 years and over (reduce at creatinine clearance under 10 mL/min).

Rupture. Emergency. Resuscitation with blood and permissive hypotension (systolic pressure 70 to 90 mm Hg) in a non-pregnant patient, then emergency embolisation or laparotomy with ligation and splenectomy. Avoid anticoagulation.

Pregnancy.

• Elective repair before conception when the aneurysm is known.
• Found during pregnancy: endovascular repair in the second trimester, or surgery when it is not feasible, with obstetric and vascular teams and shielding.
• Rupture: emergency laparotomy and caesarean section when the foetus is viable, with massive transfusion.

Portal hypertension. Embolisation is preferred, with care over variceal bleeding and splenic infarction. At liver transplantation, the aneurysm is ligated or embolised.

Medical therapy. Blood pressure under 130/80 mm Hg. Use labetalol, modified release nifedipine or methyldopa in pregnancy. No drug reduces growth.

Monitoring. After embolisation, imaging at 1 month and 6 months, then yearly. Platelet count after splenectomy. Ultrasound each trimester in pregnancy when a small aneurysm is observed.

Referral and escalation. Refer to vascular surgery or interventional radiology. Emergency for rupture or any aneurysm discovered in pregnancy.